Doctors discovered the clot Sunday while performing a follow-up exam. She was admitted to a New York hospital and is currently being treated with anti-coagulants. The Secretary of State, 65, will remain hospitalized for at least the next 48 hours so doctors can monitor the medication.

"Her doctors will continue to assess her condition, including other issues associated with her concussion," her spokesman, Philippe Reines, said in a statement. "They will determine if any further action is required."

Clinton fainted and suffered a concussion in mid-December when she was home recovering from a stomach virus. The concussion was diagnosed on Dec. 13, and she was forced to cancel several trips.